Boxing may be on the margin of the sports landscape, but every year, you’ll see a few fighters among the highest earning professional athletes in the world.

Today, you have two, Floyd Mayweather—when he’s not in jail—and Manny Pacquiao, when he’s not running for some political office in the Philippines.

But there are also some players in boxing that still generate serious cash. Some are behind-the-scenes players that the general sports public is not aware of, though hold very lofty positions in the boxing world, and if you’re associated with them, you’ll become a cash cow—because they’re cash cows.

Here’s a look at a handful of boxing’s cash cows:

1. Floyd Mayweather

It’s taken a little time, but “Money May” is finally worth, and draws, the kind of money he thought he’d originally generate when he first turned pro. According to ESPN The Magazine, Mayweather was “the highest-earning athlete in the United States in 2011, grossing an estimated $40 million, stemming from one fight, his September 2011 thrashing of Victor Ortiz."

Mayweather topped the list of highest-earning American athletes in 2011, overcoming tumultuous outside-the-ring messes along the way. Still, he’s the one main man American sports fans have come to recognize.

Like it or not, Mayweather is the face of boxing. That face attracts fans.

2. Manny Pacquiao

“Pac-Man” pretty much has the Philippines in his back pocket. He owns the nation. One day, he may rule it. For the time being, Pacquiao has more commercial appeal than any American fighter. And yes, even more than you, Floyd Mayweather, based on his genial personality and easy-going way he carries himself.

Watch out. The grave concern is 10, 15, maybe even 20 years from now Pacquiao becoming a cautionary tale, when it begins to surface that the Filipino fighter who was once dirt poor is once again dirt poor.

3. The Klitschko Brothers

Wladimir and VitaliKlitschko, who own the heavyweight division, should stay in Europe and never fight in the United States again. They don’t need to.

According to Forbes Magazine, Vitali’s net worth is an estimated $65 million and Wladimir has already made $28 million alone in 2012 as of June.

They can fill almost any 60,000-seat soccer stadium throughout Europe, though they’re primarily based in Germany.

There is a conveyor belt that feeds the Klitschkos a steady diet of mediocre American heavyweights who simply cannot compete with them.

Kevork Djansezian/Getty Images

Oscar De La Hoya knows the future of boxing when he sees it--and that's Canelo Alvarez.

4. Canelo Alvarez

The Latin fight fan is a major force in the economic drive of the sport. No one figured this out faster and still does today than Bob Arum.

It’s an Arum page, however, that Oscar De La Hoya and his Golden Boy Promotions has ripped away and follows to the letter.

That’s why they nailed down Alvarez. He’s unique in and out of the ring. He’s a red-headed, freckled Mexican who doesn’t speak a speck of English, but has a great work ethic—unlike another fellow young Mexican with a big name and little else—and can fight.

Alvarez is a future superstar in the sport and there is a reason why Bob Arum has avoided a Julio Cesar Chavez Jr.-Alvarez confrontation. That’s because Arum is too smart: He knows his cash cow, Chavez Jr., would get his ass kicked by Alvarez.

5. Al Haymon

He may not define the term “cash cow” on the strictest meaning; but everyone he touches and everyone he manages is, or will become, a cash cow.

Haymon manages Mayweather, who already had the talent and ability to reach the heights he is today. However, Haymon’s golden touch has steered talented fighters who were once unknowns, like Danny Garcia, to great fertile grounds. If you’re a budding fighter with talent—you sign with Haymon.

He doesn’t push himself out front. He just knows all the right players, and those honchos certainly listen to him.